Aftermarket tach problems

[tannerman]

Anyone tried to hook up an aftermarket tach from the pcm output signal?
I have an 04 GTO engine and pcm in a 1989 chevy truck (about 500 ponies):rockon: The tach will not read pcm output signal and I have tried changing it to 12 volt and still no response. It does pulse my led tester though. Any clues why???

[Biggsy]

Most output signals are a relatively "clean" pulse and are not enough to trigger some after market tach's (they like bigger, sharper pulses, eg in the EFILIVE logo)

I have made an interface that takes the clean signal and use it to trigger a mini coil on a circuit board using a transistor. (like a mini coil and points setup)
The output will fire most (if not all) aftermarket tacho's.

[tannerman]

I thought about doing that also, I was hoping I was just missing something in the pcm setup. I am already on it.

[s10mods]

have a look at this. I have not had a chance to get the resistor yet but it sounds like it works.
http://www.ls1tech.com/forums/showthread.php?t=544193

[cliffy v]

I had to wire my tach in 4 cylinder configuration

[eboggs_jkvl]

I had to wire my tach in 4 cylinder configuration

That would be my first question. The LS engine needs to be set for aftermarket tachs as a 4 banger.

[wait4me]

If you call the manufacturer of your gauge, they will be able to get you the converter you need to make it work.

Sometimes you can make it work by changing the tach pull up selection in the system tab on efilive.